Small Tracts Conveyance Act This bill requires the Director of the Bureau of Land Management (BLM) for a state (respecting certain public lands) or the Regional Forester with jurisdiction over the National Forest System (NFS) land of a specific Forest Service Region (respecting certain NFS lands) to select an eligible federal lands parcel for conveyance: (1) in response to a request by an adjacent landholder (any holder of non-federal land that shares one or more boundaries with such a parcel and who requests to purchase such a parcel), or (2) upon the recommendation of the BLM District Office or NFS unit that exercises administration over such parcel. The Department of Agriculture and the Department of the Interior shall each create a process by which an adjacent landholder may request to purchase an eligible parcel. A conveyed eligible parcel may not exceed 160 acres unless the BLM or the Forest Service approves a request for additional acreage. An adjacent landholder may only acquire one eligible parcel a year, subject to an exception. The BLM or the Forest Service, as consideration for the sale of an eligible parcel, shall require a cash payment that is equal to at least the fair market value of such parcel, including the mineral estate, being conveyed. The purchaser of an eligible federal lands parcel under this bill shall cover the costs to be incurred, or to reimburse the BLM or the Forest Service for the costs incurred, in carrying out the conveyance. A conveyance of an eligible federal lands parcel under this bill is categorically excluded from the requirement to prepare an environmental assessment or an environmental impact statement under the National Environmental Policy Act of 1969.